Ultrasonic NDT Prototype for the Inspection of Ducted Post Stressing Tendons in Concrete Beams

There is worldwide concern about concrete bridges which derive their strength from post stressed steel tendons in grouted ducts. Problems arise when grouting has not been carried out properly, since the combination of voided regions and moisture penetration can cause corrosion of the tendon and catastrophic failure of the structure [1]. Post tensioned bridges built during the middle of this century are particularly susceptible and there is a pressing need for a cost effective non destructive means of assessing the condition of the embedded ducts and tendons. In response to this problem, a track mounted ultrasonic scanning system ‘CANDI’ (Cable Analysis by Non Destructive Inspection) is currently under development in UMIST, and this work describes the CANDI prototype and results obtained

Edge Weld Penetration Assessment via Electric Current Deflection Measurements

Because of the awkward and somewhat irregular shape of the weldment, conventional methods [1] could not be adapted to the nondestructive measurement of GTAW edge weld penetration on clamshell-style catalytic converters and a special inspection system based on the electric current deflection method was developed. DC or low-frequency AC electric resistance measurements, also known as the Potential Drop Method (PDM), are well-developed for plate thickness assessment and crack detection [2–6]. The operating principle of these methods is that, under certain arrangement of the electrodes, the defect or crack in a conducting specimen will cause a measurable increase in resistance between given points compared to the situation without the defect or crack. In recent years, this simple contact technique was largely obscured by more sophisticated noncontacting eddy-current techniques especially in industrial applications. In this article, we demonstrate the distinct advantages of the Potential Drop Method through the example of GTAW edge welds where the awkward shape of the specimens and the required large penetration depth render the eddy-current method less feasible.</p

Draft Definitive Statement on the Significance of Mis-match of Strength in Welds

Surface somatosensory evoked potentials (SSEP) collected from conscious subjects usually presents poor signal-tonoise ratio (SNR), requiring several hundreds ensembles averaging to provide a meaningful waveform. A FPGA based adaptive filtering is proposed to perform fast and accurate SSEP extraction by fixed-point adaptive noise canceller (ANC). In 6 normal subjects and 1 neurological abnormal patient, the latency and the peak-to-peak amplitude in SSEP by FPGA based ANC technique were compared with that measured by ensemble averaging. Using 100 trials ANC processed SSEP was sufficient to extract a waveform in equivalent to that extracted by 1000 trials ensemble averaging. The use of fixed-point ANC based on FPGA proved to shorten SSEP measurement time and provide varying information underlying SSEP. ©2009 IEEE.link_to_subscribed_fulltex

A compliance-based approach to measure fracture resistance curve for surface cracked steel plates

10.1007/s10704-013-9850-3International Journal of Fracture18211-1